Conduit clamp for knock-out boxes



Jy 16, 1929. .N. O. HOUHTON .1.721,1l9

CONDUIT CLAMP FOR KNOCK-OUT BOXES Filed Oct. 30, 1926 I O 0 O 0 I? qZjwuewtoz Fig. 5 JVoman 0. ffozg/z ton Patented July 16,1929: 1

j UNITED STATES LPAT'E'N T oFl cE;

NORMAN-o. Ho'UsH'roN, on WASHINGTON, msrrnfor or COLUMBIA.

' CONDUI'I CLAMP FO R'KNOCK OUT BOXES;

. Application filed October so, 192 Serial No. 145,166."

This invention relates to an improved clamp for securing electricconduits to outlet boxes, and has particular reference to such" a clampadapted to effect a rigid connection between such outlet box and thecon,-

I duit.

An important object of-the invention re sides in the provision ofaclanip as above noted having means for effecting a, posiother highlyobjectionable features which duit in clamped position;

. plan view of the 10 tive ground connection between the conduit and theoutlet box.

Much difliculty has been experienced 1n providing a suitable connectionfor electric conduits whereby such connection may be made without thenecessity of removing the outlet box'as is now the case where bushingsare employed, and it was this and the applicant seeks to overcome. Theconnection to behereinafter described. will afford a most rigid supportbetween the 'outiet box and the conduit, while at the same timeproviding a positive groundconnection therebetween.

A further object of the invention resides in the provision of a clamp ofextremely simple construction, unusually cheap of man-' ufacture,strong, durable and highly efficient in use.

Other important objects andadvantages of the invention will be apparentduring the course of the following descriptionreference being had to theaccompanying drawings, in which like numerals are employed to designatelike parts throughout.

Referring to the drawings,

Figure 1 is a perspective view of a comthe invention, v

Figure 2r is a sectional :view illustrating the method of attaching theclamp to the outlet box,

a similar view with the con- Figure 4 is a bottomcomplete clamp, and,

Figurefi is an inner .face view of one half of the clamp.

- Referring specifically tothe drawings, the

numeral 1O designates my improved clamp as a whole, formed in sections11 "and 12. i

As clearly shown each section is formed semicylindrical and providedwith a pair of integral apertured ears -'13 and 14, the ears 13 havingenlargedsmooth bores or forked as shown, while the ears 14 are drilledand tapped for the reception of draw bolts 15. i

It willbe noted that the two parts are formed identical, which willavoid the necessity of using care in selecting any pair of sections forassembly. I

As clearly shown, the inner faces of the clampsections arev formed uponan are, as

at 16, with'the thickest portion of the material adjacent the bottom ofthe section. This arcuate face is provided with a plurality of 'pointedlugs 17', any desirable numher being employed, and these lugs areadapted,to engage-and bite into the metal of the conduit at assembly. Thepurpose of the arcuate faces is to provide a suitable fu crumf forspreading the lower ends ofthe sections, and it will be obvious thatafter a conduit hasbeen insertedwithin the clamp and the bolts 15 drawnup tightly, a'rolling action will have been imparted to the sections 11and 12 due to the arcuate faces 16, such actionobviously causingthe-lower ends of, the sections tomove outwardly.

Means areprovided for rigidly securing the clamp within the conventionalknockout box openlng, and this means is m the form of segmental groovedflanges 18, formed integral with the lower ends'of the sections 11 and12. It-will be seen by reference to Figure 4 that the bottom of thegroove is concentric withthe body of the sections 11' and 12, while theflanged portion 19 de creases in depth toward the sides, finally merginginto the main or straight portion ofthe flange 18, as at 20. It will beobserved that the portion 19 is flush with the outer' faces of'thesections 11 an d 12, while the concentric line-of the groove is justsulfi- -ciently small to enter the conventional knock-out opening Thesections 11 and 12 are slightly spaced at assembly so as to per- .mitthem' to readily fulcrum; upon the faces 16. The forming of the flanges"18 provide I shoulders 21, and these shoulders are adapted to receivethereon the end of the conduit to be clamped, and act as ameans'to limitthe insertion'of such conduit Within the clamp. 1- The operation of thedevice is as folows:-

A pair of clamp sections 11 and 12 are brought face to face. clined awayfrom each other at their upper ends so as to permit the insertion of theflanges 19 through the knock-out opening 22 of the outlet box 23, itbeing understood They are then inthat the widest portions of the flanges19 have a greaterdiameter than the openings 22. The sections are thenbrought together I causing the flanges 19 to engage beneath the edges ofthe opening 22. The bolts 15 5 are then inserted within their respectiveears and the device is ready for the conduit 24. The conduit is. theninserted between the sections 11 andf12 until its lower end rests uponthe shoulders 21.. The bolts 15 are to the arcuate faces 16. Acontinuous tightening of the bolts 15 will cause the pointed lugs 17 tobite into the metal ofthe conduit '24, thus providing a very positiveground connection. while at the same time providing a very rigid meansfor preventing dis-- placement of the conduit. .The powerful binding ofthe flanges 18 and 19 against the 1 edges of the opening 22 alsoprovides a very eflicient ground connection togthe box 23. Thisgrounding of the conduit and outlet box is essential in the installationof Iawir-x ing system, and is required by the laws governing suchinstallation. v K It will be obvious from the foregoing that anexceedingly practical and efficient clamp has been provided, one thatmeets the re q'uirements in its particular class of work in a highlysatisfactory manner. The device in addition to its cheapness ofmanufacture, will save a considerable amount of labor expense ascompared with the 'old'type of clamping where ,a bushing. connection isemployed; g It is to be understood that the invention is not limited tothe precise construction set forth, but that it includes within itspur-" view whateverchanges fairly come within either the terms, or thespirit of the appehded claims.

Having described my invention what I 'claimiszv I 1. A device of thecharacterdescribed for clamping theend of a conduit,'comprising aitwopart clamp having lower flanged ends l a. v

.for engagement oven the edges of an opening formed in an outlet box,the inner sur'-' faces of said two-parts so shaped as to impart afulcrum action thereof upon the sides of the conduit whenthe clamp isforced into clamping engagement with the conduit, said fulcrum actioncausing the 'jlOWGI flanged ends to rock outwardly into firmengage mentwith the edges of the opening, means for drawing together said two-partsand grounding means adapted to pierce. the metal of the conduit duringclamping.

2. A-device of the character described for clamping an electric conduitto an outlet box, comprising identical co-acting clamping elements,- theinner clamping surfaces ofwhich are formed upon an arc longitudinally,piercing elements formed upon said surfaces, flanges formed upon thelowerends of saidelements, said flanges terminating t adjacentthe sidesof the elementsfor form ing a straight'vertical portion, means forforcing said elements into clampingengagement with the conduit, saidforcing action resultinglin a rolling or fulcrum movement of the arcuatesurfaces upon the sides of the conduit causing the lower flanged ends torock outwardly linto firm engagement with the edges of anopening'fo'rme'd in the outlet box, said action further causingsaidpiercing elements to pierce the metal of the conduit. 3. Aconduit'clampfor use in connection with outlet boxes having an openingfor'med 95' therein, comprising a pair of identical coacting clampingmembers having longitudinally arcuate inner surfaces proportioned "tocontact. with the walls of a conduit, pointed lugs formed upon saidarcuate faces, grooved flanges formed upon said'members' 'attheir lowerends, ,said grooved flanges terminating in s traight'vertical portionsadjacent the sides of the members, apertured. ears formed upon saidmembers at their upper ends, draw bolts engaging said ears, said groovedflanges adapted to engage over the edges of the opening of said outletbox,

said members when drawn tovs'ardv each other at theini: upper endspartaking of a j fulcrum motion upon said arcuate surfaces for spreadingthe lower flanged ends of said members whereby said flanges will firmlyengage the edges of said opening, said fu1-- crum and clamping motioncausing saidpointed lugsto bite into the metal of the conduit. i i

In testimony wh f affix' my ign? Y,

Y ivoRMAu o. HOUGHTON. v 1

'ture.

